Spinning of viscose



Dec. 26, 1950 N. L. cox 2,536,014

SPINNING 0F VISCOSE Filed Dec. 14, 1946 IN VEN TOR. NORMANLOUIS COX BY04m! 6 ATTORNE Y Patented 26,1950

SPINNING or vrscose Norman Louis Cox, Claymont, Del, assigns: to

, E. I. du Pont de Nemours & Co

mpany, Wilmington, Del., a co ration of Delaware Application December14, 1946, Serial No. 116,415

23 Claims. (CI; 28-82) This invention relates to the regeneration ofcellulose from viscose. More particularly, it relates to a new processfor manufacturing regenerated cellulose articles such as filaments orfilms having improved properties.

Although the invention is generally applicable to the preparation offilaments, yarns, films, caps, bands, ribbons, and other structures orregenerated cellulose, it will be discussed with particular reference tothe production of viscose rayon yarn.

It is known that the general strength and quality of viscose yarns areimproved through reduction of the primary swelling of the gel fibers.The great importance of the gel swelling factor in viscose spinningoperations has attained full recognition only in the last few years(see, for

tionately high salt index values) has been thought desirable ontheoretical grounds for viscose spinning. A further problem, then, is tomake unripened viscose of high salt index amenable to example, U. 8.2,347,883 and 2,347,884) It is now recognized that, to constitute acommercially useful viscose rayon process, the viscose composition andthe composition of the sulfuric acid coagulating bath must be sobalanced as to, permit the production of regenerated cellulose filamentshaving a gel swelling factor of not more than about-6.5. It has beenfound that, for a given viscose, yarn properties such as tenacity,elongation, softness, etc.. are, as a rule, best when spinning is doneat or near the point of minimum gel swelling. It has been found,moreover, that yarn properties are improved through methods designed toreduce the gel swelling factor below the above-mentioned value of 6.5and spinning. This is highly desirable since the use of unripenedviscose would result in decreasin or eliminating the ripening time nownecessary in manufacturing practice. Accordingly, methods for furtherreducing the gel swelling factor of unripened viscose. and inparticular, methods involving further improvements in yarn propertiesare particularly desirable.

.An object of this invention is to provide a process of manufacturingregenerated cellulose filaments having gel swelling values lower thanheretofore attainable and exhibiting considerably improved yarnproperties. Another object is to provide a process whereby unripenedviscose can be spun in conventional spinning equipment to give yarn ofhigh quality. A further object is to provide a process of manufacturingregenerated cellulose yarn having entirely novel and desirableproperties. Yet a further object is the provision of a high tenaci y.high fatigue resistant regenerated cellulose fiber having anoncrenulated surface and having improved soil and abrasion resistance.Other objects will appear hereinafter.

These objects are accomplished, in accordance with the invention, byextruding viscose into a sulfuric acid-sodium sulfate coagulating bathcontaining zinc sulfate and stretching the filament, preferably in asecondary bath, the coagu- It is well known that unripened viscoses (theing of green viscoses, even though their high delation of the gelfilament being carried out so that it is in contact with small amountsof a water-soluble organic quaternary ammonium compound. i. e.,hydroxide or salt. in which each of the four organic radicals attachedto the nitrogen contains not more than four aliphatic carbons, at leastthree of these organic groups being completely aliphatic and the fourthone, when aromatic, containing only one benzene nucleus, said quaternaryammonium compound having no appreciable surface tension loweringproperties.

Another object, which it was unexpectedly found possible to accomplishthrough the invention described below, was the production of very highstrength yams having smooth (non-creme gree of xanthation (which isreflected in proporso lated) surfaces. These yarns have substantiallywhich can be used for that purpose must be surface-active. This means,in terms of chemical constitution, that such quaternary ammoniumcompounds must have at least one long chain alkyl group of at least 6,and preferably at least 12 carbon atoms. The prior art did notcontemplate, and, in fact, positively excluded, the use of non-surfaceactive, short-chain quaternary ammonium compounds, which are, indeed,ineilective for the purpose of preventing'spinneret incrustation. Therewas, therefore, no reason to expect that the non-surface-active,short-chain compounds would have any eflect whatever on viscose spinningand/or yarn properties, and even less reason to expect that their usewould decrease the gel swelling factor of the yarn below any'previouslyknown minimum and permit the production, from either ripened orunripened viscose, of high tenacity filaments possessing certainentirely new properties. That these advantages are, in fact, obtainedthrough the use of non-surface-active, short-chain quaternary ammoniumcompounds is particularly remark able since the similar, but long-chain,surfaceactive compounds of the art are incapable of producing theseresults. This indicates that the quaternary compounds used in thisinvention are highly selective viscose or bath modifying agents and thattheir use provides solutions to the several problems outlined above in asurprising manner.

By the term "water-soluble, non=surface-active quaternary ammoniumcompounds" is meant those quanternary ammonium compounds which, inconcentrations of 0.1%, do not lower the surface tension of distilledwater at 25 C. by more than about 6 dynes per centimeter. Suchquaternary ammonium compounds may contain four aliphatic groups attachedto the nitrogen atom none of which groups are more than a carbon atomsin length or they may contain three of;

such groups, the fourth group being then arc;

matic and containing only one phenyl group.

The anions in every instance are devoid of sur- 5 all determinedaccording to the following pro-- cedure. The gel thread was collected ina monolayer on a bobbin, by manually operating a traverse mechanism withthe thread being stretched 80% in the hot dip bath. The sample wascentrifuged (1400 R. P. M.) for one minute, out off, and weighed in aclosed bottle. The sample was washed free of acid, dried in an oven a1o5 6.,

' droxlde and the free sodium hydroxide and that I and weighed. Theratio of the gel weight to cellulose weight (grams of gel per gram ofcellulose) is referred to as the gel swelling. Variations may beintroduced in the procedure, e. g., in the stretch, spinning speed, orlength of bath travel, but these introduce only minor changes in thenumerical values of gel swelling.

Another important indication of yarn quality is the factor referred tobelow as D value. This factor relates to the rate of neutralization ofthe viscose filament in the coagulating and regenerating bath. It isdetermined by adding to the viscose a suitable indicator, in this casebromocresol purple (pH range 5.2 to 6.8), and observing the distance ininches from the spinneret at which point the purple color completelydisappears in the traveling filament. This distance is the D value. Theselected quaternary ammonium compounds suitable for use in thisinvention reduce the rate of neutralization of the spinning filaments,hence increase the D value over that of unmodified viscose. It has beenfound that, in general, the greater the D value or the slower the rateof neutralization, the better the yarn properties. It is believed thatthe increased D value is an indication that the modifying agents of thisinvention permit greater dehydration of the viscose before the gelstructure of the filament is permanently set.

In the following examples parts and percentages are by weight. Theseexamples are given for illustrative purposes and are not who construedin any sense as limitative.

EXAMPLE I hours using 35% CS: (based on the recoverable.

bone-dry cellulose). Xanthated crumbs are dissolved in a solution ofcaustic containing the modifier in the amounts mentioned above. Aftermixing 1 hours at 0 C., the freshly prepared viscos is filtered while itis cold, deaerated, and kept at 0 C. until spun. It is spun in theunripened state, as shown by the high salt index values, high xanthatesulfur content, and low sodium trithiocarbonate content. In allexamples, the caustic content of 6% refers to the total alkalinityexpressed as sodium hydroxide. It includesv the benzyltrimethylammoniumhycombined in the form of sodium carbonate, sodium trithiocarbonate, andsodium cellulose xanthate.

The viscose is spun into 275 denier-100 filament yarn by extrudingthrough a spinneret havlog holes of 0.0025-ipch diameter into primarycoagulating and regenerating baths comprising (1) 6.0% H2504, 14%Nazsoi, and 15% 21180.4. and (2) 9% H2804, 22% NazSO4. 1% ZnSOr, and 5%W804. The yarn is given a bath travel of 28 inches by using a rollerguide. The apparatus and general procedure used to lead viscose into thebath and to collect the formed thread are essentially the same as thoseused commercially in the so-called bobbin or spool process. The specificconditions include a bath temperature of 58 C. and a first feed wheelspeed of 485 inches per minute. The filaments are carried through awater bath at 95 to 100 C. and wound up at such a speed as to give 80%stretch beyond the feed wheel. The resulting regenerated gel yarn iswashed free of acid and salt and then x processed. The yarns which aredried on the bobbin or, alternately, partially relaxed before drying byrewinding on another bobbin, are twisted 4 turns per inch and testedafter conditioning at 21 C. and 60% relative humidity for 48 hours.

The properties of the yarn prepared from the viscoses described hereinare listed in Table IA together, for comparison, with those ofunripened. unmodified viscose and of ripened, un- 15 per 100 grams ofviscose. Both yarns of Fig. area 1 and 2 were prepared using acoagulating bath designated as The skin of regular viscose yarn may beshown very graphically by a special dye technique. When the crosssections are soaked in 0.2% Pontamine Sky Blue dye for to 60 minutes,the core takes on a deep blue color while the skin remains undyed.However, with yarns: from viscoses modified with quaternary ammoniumsalts, the dye boundary is diifused and no great contrast in shadesbetween the skin and core is visible, as is shown in Figure 2.

Table L4.

Modifier Elongation. Per E Salt {2" f g"; News, i li-l Cent SGelI rampan a mo 5 we a no Index Sum. Per Cent 100 8. ing in.

Viscose Dry Wet Loop Dry Wet Loop COAGULATIN G BATH 844- (H'lSOPNinSO-ZnSOQ COAGULATING BATH 8.5-22-1-5 (HasO4--NazSOz-ZnSO FeSO4) 8+ 1. 0.630 i 3. 44 1. 76 2. 25 9. 5 l6. 0 7. 4 3. 53 2. 2 8+ 1. 40 0.60 0.78 3.70 2. 43 2. 7. 9 19. 8 4. 6 2.64 5.0 8. 1 1. 40 0. 70 1. 50 3. 60 2. 402. 20 7. 0 18. 4 3.6 2. 65 6. 0 8. 6 1. 35 0. 72 9.0 3. 9i 2. 2. 30 8. 015.2 4. 1 2. 66 7. 0 5. 0 1. 15 l. 30 0 3. 70 2.29 2.0 7. 7 18. 1 V 3.43. 52 2. 2

modified viscose (the standard viscose of commercial operation), bothcontrols being spun under conditions identical to those for the modifiedviscoses. It will be seen that the level of properties is lowest for theyarns from the unripened, unmodified viscoses. wet strengths of yarnsfrom the unripened, modified viscoses of this invention are greater thanthose for ripened. control viscoses.

The yarn produced by this and the other examples has a number ofremarkable properties which distinguish it sharply from otherregenerated cellulose yarns. The most readily apparent of these newfeatures are the cross-section and the surface. The cross sections ofviacose yarn are observed and studied in the following manner. Afterimbedding the yarn in paraflln, cross sections are cut and affixed to aglass slide bya shellac cement. After removing the paraffin in xylene;the sections are swollen in water and photomicrographs are taken. Foryarns prepared from unripened. unmodified viscose spun into zinc baths,a skin or outer shell which swells to a different extent from that ofthe core is visible. These yarn cross sections show both deep andshallow crenulations around the contour of the filament, as shown inFigure 1. However, for yarns of this invention, as, for example, thosespun into zinc baths from viscose modified with non-surface-active"quaternary ammonium compounds, the boundary between the skin and coreis very diilfuse and crenulations are absent, giving the yarn a smoothsurface, as indicated in Figure 2. The yarn of Fig ure 2 is unripenedviscose obtained using 9 millimoles of benzyltrimethylammonium hydroxideIn allcases, the 5 The filaments of this invention having smoothsurfaces, i. e., showing no appreciable crenula- .tion, have outstandingresistance to soiling, flbrillating, and laundering. Fatigue resistanceis also materially improved.

The yarn from viscose spun in contact with the modifiers of thisinvention differs from regular viscose yarn in five other respects: 1)the density appears to be higher than that of normal viscose yarns ofthe same orientation; (2) the yarns of 0 this invention behavedifferently when :flbrillated eral order of less than 35, i. e., about 5to about 35; a secondary swelling of less than 35%, i. e., about toabout 85%; and less than about 40% core, the skin varying from about 60%to about 100%. As the amount of skin approaches 65 100%, the amount ofcore becomes negligible and the diffuse boundary is diflicult to bringout by the dyeing technique, the negligible-core yarns, obtained, forexample, by Example III or X and described and claimed by thisinvention, still being characterized by lateral orders, secondaryswellings, etc. which distinguish them from other yams as pointed outabove. In the following Table 13, the physical characteristics of yarnsfrom modified viscose in comparison with other known yarns are shown.

where 11 is the 101 interference intensity and 1:11 is the minimumintensity hetween the 101 and the 101 interferences. The orientation isgiven by the expression.

i am) where In is the 002 interference intensity and 190(3 is the sameat 20 from the equator.

EXAWLE H A 7-6 viscose (7% cotton linter cellulose-6% total sodiumhydroxide) modified with 1.5 milli and cord strength and fatigueresistance of the cord over warn produced from normally ripened viscosespun under identical conditions.

Table 18 Skin Cross-Section X-Re Data Tenaciyt' Flbril- Secon- Dye AbyFatigue g. per denier Fiber lotion Dendary sorption Resist- B cResistsity Sgell- Ralte, L 1 i 13111108, Per Cent oun- ,renuonce g m n.store 1 enrs. Approx. dory lotions Contour Order tation Dry wet I Fromunripened vis- 60 Diffuse.- None. Oval to Great. 1.92 72 8 1S 7. 4 50+3.8 2.7

cose; benzyltri- Round. methylammonium hydroxlde modified Example I. 2Control; unripvned, 30-40 Many Irregular 86 13 7.0 3.7 2.2

unmodified viscose. 3 Controkripened, un- 60 .do. do 93 13 6.0 3.4 2.2

modified viscose. 4 Cox-dare" 287 (tire 50 .do... do.. Little- 1.23 8829 8.1 25 3.7 2.4

cord yam). 5 Textile Cordura... -30 do. do. 109 34 6.0 2.5 1. 5 6Cordura" 540 (ex- 60 .d0 d0 Little- 1.17 97 ll 7.5 3.9 2.5

perimental). 7 Lilienfeld yarn. None Noue Round. 1 11 7.0 3.2 1.4 8"Fiber D (U. S. P. None... d0 0"... 100+ 33 2.0 1. 1 0.6

2, 249. 745). 9 Bemberg yam None do do... 98 0.7 44 5.0 1.8 0.8 10Standard textile yarn 20-40 Many. do 17.5 38 3.0 2.0 1.0

In the above table, the dye absorption rate Table II refers to the timein minutes required for the absorption of of the dye by 5 gram y YamProperties Unripened Ripcned from a bath consisting of 250 grams ofwater, 30 Modlfled Unmodified 0.1 gram of Pontamine Fast Green 5 BL and1.5

- Ten. d. D 3.80 3. 35 v c. of sodium sulfate at as" 0. Tem gj g 5 TheX-ray data are measured photometrically Ten. g./d. Loop. 2.98 2. fromfiat plate difiraction patterns, the distance $835: $3; $3 2-} betweenthe specimen and the dim losing 5 cm. 35 glo n g. 11in Cent Loop. cg goThe lateral order, which is a measure oi crystaltj gg m-g g g $1 1.linity, is given by the expression Cord Proparhea Conditioned Ten. gJd.3. 51 3.07 Oven-dry Ten. g./d 3.98 3. 46 i- 10 W69 Fatigue Hours 48 39EXAMPLE m A 7-6 viscose modified with 1.5 millimoles ofbenzyltrimethylammonium hydroxide per grams of viscose is prepared andspun and the yarns are processed in the-manner described in Example I.In this case, however, the coagulating bath is 8.0-23-4(HzSOe-NazSOr-ZDSOO. The physical properties of the yarns from theunripened modified viscose are much better than for accompanyingcontrols from normally ripened viscose, as is shown in Table III.

Table III 55 Unrip'ened Ripened Yam Pwpemes Modified Unmodified Ten.g./d. Dry 3.88 3.45 Tall. g./d. Wet 2. 72 2.33 Tell. g./d. Loop. l 2. 972. 43 6Q Elong. Per Cent Dry. 7.8 6.4 1 121mg Per Cent. Wet Gel Swelling2: 61 4 "1) Value, inches (i. 0 2. 5

EXAIMPLEIV Cotton linters viscose similar to that described in Example11 is spun into filaments using all conditions for producing andprocessing as in Example I except that the acidity of the high zinc bathis increased from 8 to il H2804. The-properties of the 'yarns as well asthose of yarns from unmodified ripened and unripened control viscosesare shown in Table IV. It will be seen that the use of the modifiedunripened 7d viscose at this higher ba h a i ity gives lower selswelling and improved properties. The high spinnins speeds desirable incommercial practice require relatively high bath acidity, which in turnmeans a certain sacrifice inyarn properties because of the increased gelswelling. As shown in this example, it is possible throughmodificationoiviscosetoemployhighspinningspeedsa't high acidity withoutthe disadvantage Just mentioned.

Table IV U H Unripsnsd Ripensd m Unmodified Unmodified as. 6. Dry 4.03.86 3. 45 Ten. Wet 2. ll 2. 2. ll 'i'sn sJd. Loop as aso 1. as

.Psr Centlrry.-- 8.8 e 1.7 8.0

long. Pet (mt Wet.-. 21. l3. 6 21. 3

Zions. Per Cent Loop" 4.0 5.2 4. 1 Gsliw 274 8.12 3.46

"D" Value, in inches-.- 4. 5 i. 5 1. 5

EXAMPLE V Table V Unripened-i- Unripened-i Unripened common cinema:Unmodified 'Ien. gJd. Dry 3.00 3.82 3. 60 Ten. {.Id. Wet 2. 05 2. 72 l.99 Ten. gJd. Loop 2.70 3. ll 2. 74 Elongi'ler Cent Dry. 7. 5 8. 3 8. 5Ilong. Per Cent Wet-.- 2.4 2.3 18.5 Elong. Per Cent Loop" 4. 9 5. 8 6. 7Gel Swelling 2. 56 2. 67 3. 11 "D" Value, in inches.-- 3. l5 3. 5 1.7

EXAMPIE VI A cotton linter viscose containing 7% cellulose, 6% totalsodium hydroxide, and 2.0 millimoles per 100 grams oftetramethylammonium chloride per 100 parts of viscose is prepared asdescribed in Example I. The viscoseis spun in ,an unripened state in asulfuric acid-sodium sulfate-zinc sulfate (8-14-15) bath and allconditions of Example I for spinning and processing are used with theexce tion that 100% in: stead of 80% stretch is employedin the secondarybath. The "table below shows the improvement in yarn properties and gelswellin obtained with this modifier.

Table VI Unri Unripened smin (0 incl Unmodified 3.05 a. can 2. 2.78 2.6.7 7. 19..' 1a 4.1 e 2.31 a as 1.

Unripehcd 7-6 viscose containing 1.7 millimoles ofphenyltrimethlylammonium hydroxide per 100 grams oi viscose is spun intoan 0-14-15 (H2804--NB2SOs-ZDS O4) bath and the yarn is stretched andprocessed as in Example I. The reduction in gel swelling andneutralization rates (increased "1)" value) and the improved yarnproperties of the non-crenulated fiber thus obtained are shown in TableVII below:

Table VI! Unrioonod m nod ,Modiflsd Um diiisd Ten. gJd. Dry 3.87 3.0Ten. gJd. Wet.- 2.70 I. 'Ien. g.fd. Loop $.00 2. 74 Rims. Per Cent Dry8.0 8.5 Elong. Per Cent Wet..- 22.2 18.5 Elana. Per Cent 0.. .15 0.7 Go]Swelling. 2. 7 3. 12 "D" Value, ininchss... 3.3 1.1

'EXAHPLEVIII Cotton linters viscose containing 1% cellulose. 6% totalalkali as sodium hydroxide. and 1.! millimoles of tetraethylammoniumhydroxide per 100 grams of is prepared as described in Example I. Inthis case, however, the viscase is ripened as is done for normal viscoseto a salt index of 5.0 (-xanthate-surfur 1.1%). It is then spuninto'filaments under the conditions of Example I except that 6% insteadof 8% sulfuric acid is used in the sulfuric acid-sodium sulfate-zincsulfate bath. The same large reduction in gel swelling andneutralization rates are observed with this ripened viscose as with thegreen viscoses of the preceding examples. In addition, the wet strengthis increased and filament contours are changed as in the case orfilaments from green viscose modified with nonsuriace-active quaternaryammonium compounds. Table VIII below shows the yarn properties ascompared with a control yarn.

Table VIII Unrinened Ri nod Modified Unm diflod as; ms 115 as: 2.02 am8.0 ms 24.0 214 so as as a1 4.5 a0

7 mm 1x Cotton linters containing 7% cellulose, 6% ta caustic, and 2.8millimoles of tetramethylammonium chlorideper grams of viscose isprepared and ripened to a salt index of 5.0 as is normally done forregular visnose, and then spun into filaments using all the conditionsof Example I for collection and processing with the exception that a9-23-4 (H:S04NaS04-ZnSO4) bath is used instead of an 8-14-15 bath. Aconsiderable decrease in 'gel swelling and increase in D valueareobtained, which are reflected in a measurable increase in wet strengthof the yarn. The character oi the filament is changed in the same manneras noted with other modifiers and unripened Table IX below shows theyarn properties as compared with a control yarn.

Table iX "I d Ripened Yam Pmpmm l i d i fi d Unmodified Ten. d. Dry 3.l7 3. Ten. Wet 2.20 3. Ten. gJd. Loop 2., .0 6. Elong. percent Dry 13.8m. Elong. percent Wet 3. Elong. percent Loop.. ll 3. Gel Swelling a G1"D" Value, in inches 5 2.

LE X

yarn are compared in Table X below with those of control-spun into anidentical bath except that the quaternary ammonium compound is omitted.The same large reduction in gel swelling, increase in neutralizationrates, modification of filament, contour, and improvement in strengthare observed as when the modifying agent is added to the viscose. a

Table A! a on (1 a! memes Ett Ea Ton. g./d. Dry Ten. g./d. Wet 'lcn.g./d. Loop. Elong. Percent Dry. Elong. Percent Wet Elana. Percent LoopGel Swelling I "D" Value, in inches A 7-6 viscose is prepared asinlhxample I except that the modifier is tetraethaholammonium hydroxide,(OHCHzCHz) 4i-NOH used in concentration of 1.5 millimoles per 100 gramsof viscose. The viscose is then spun in the unripened state, using theconditions described in Example I. Similar improvements are observed, asshown in the following table.

Table XI Unripened Um-lpened Modified Yarn Properties Unmodified fibersspun from normally ripened viscose.

Ten. g.ld. Dry Ten. g./d. Wet

Bwellin "D" Value, in inches In copending application, filed by N. L.Cox on March 22, 1946, with Serial -No.'656,478, it is.

shown that addition of small amounts of alkali trithiocarbonate tounripened viscose permits spinning the unripened viscose, to give fiberswith properties comparable or superior to those of It has now been foundthat the alkali trithiorcarbonate modification can be combined withfurther advantage with the treatment described in the precedingexamples.

- 12 To a 7-6 viscose prepared as in'Bxamplo I is added 1.5 millimolesof benzyltrimethylammo- .nium hydroxide per grams of viscose and 0.44%of sodium trithiocarbonate. The viscose is spun in the unripened stateunder the conditions of Example I, using a sulfuric acidsodiumsulfate-zinc sulfate (8-15-15) both. It will be seen from the tablebelow that the D" value of this viscose having a combination ofmodifiers is far greater than that of viscose having onlybenzyltrimethylammonium hydroxide. in the same amount, as modifier.Furthermore. the D value is at least equal and, in general, superior tothat of a viscose ripened to the same trithiocarbonate content as themodified, green viscose and containing the same amount of quaternaryammonium compound modifier.

Table XII Unripcned r b ned Rlpmsd wi zi i fi fisi Mixllfled ModlflodYarn Properties. andwithwith-- Benzyltrimothylsmmonium Hydroxide PercentNmCSz, total. Ten. gJd. D

The modifying agents suitable for the purpose of this invention arequaternary ammonium compounds having the gross formula wherein X is ahydroxyl group or an anion having-no surface activity, e. g., thechloride, bromide, iodide, sulfate, bisulfate, acetate, ctc., anions,and the radicals R1. Ra. R: and R4. are organic groups having not morethan four aliphatic carbons, at least three of these radicals beingcompletely aliphatic and the fourth one. when aromatic, containing notmore than one aromatic (benzene) nucleus. All R groups may be aliphaticand in that instance they may be alike or different. A chemicalstructure involving only short aliphatic chains or only one ammaticnucleus is intimately connected with the absence of surface-activeproperties in the ruodi-y.v

l3 nary ammonium compounds. The first six mem. bers of the table areshort-chain compounds, 1. e.. compounds having no aliphatic chain longerthan four carbons or no aromatic chain longer than one benzene nucleus.It will be noted that they have substantially no surfacetension-lowering effect. In comparison, it will be seen that surfaceactivity becomes appreciable with a six to eight carbon chain, and isvery high with compounds having twelve or more carbons in a chain.

Table XIII TSui-fiaco fliiflrwntre ens on, rom a r, Mqdmer d dynes percm. per cm.

Tetramethylammonium chloride 72. 3 0. 3 Tetraeth lammonium hydroxide":60.8 5.8 Tetrah oxyethylammonium hyd xide. 67. 5. l Totrabutylammnniumiodide 67, 4 5. 2 Phenyltrirnethylammonium hydroxide. 71.4 1.2'Benzyltrimethylammnnium chloride 72. 5 0. l Hcxyltrimethylammoniumbromide..- 03. 8 8.8 Oct ltrimethylammonium chloride 64.0 8.6 Decyltrimethylammonium chl ride... 37. 7 34. 0Hendccylbenzyldimethylammonium chloride 37. 7 34. 0 Water; 72.6

The critical importance, for the success of the method here described,of using materials essentially devoid of surface tension-loweringproperties is effectively demonstrated by substituting for theshort-chain quaternary ammonium compounds a similar material having along aliphatic chain and, therefore, surface-active. For example. theuse in viscose of dodecyltrimethylammonium chloride at a concentration(0.38 millimole per 100 grams of viscose or 0.1%) comparable on a weightbasis with those used in the above examples produces no appreciabledecrease in gel swelling, no increase in D value, and no change in thephysical characteristics of the yarn, e. g., in filament cross section.Increasing the concentration to one comparable on a molar basis withthat of the examples (1. e., up to 1.3 millimoles per 100 grams r 0.33%)only makes matters worse since it causes an excessive increase in thevicosity of the viscose coupled with extreme difficulty of deaeration,and gives yarn having inferior properties as compared to control yarn.

In terms of chemical structure, the preferred modifiers for use in thisinvention are those in which all four organic groups attached to thenitrogen atom are hydrocarbon groups or bywhich the radical X ishydroxyl or halogen of atomic weight above 19, i. e., chlorine. bromine,

or iodine. The most useful modifiers are the" quaternary ammoniumhydroxides having a total of. not more than ten carbon atoms in themolecule and in which all organic groups are hydrocarbon orhydroxyl-substituted hydrocarbon. An obvious requirement of themodifying agents is that they be soluble in the viscose or in thecoagulating bath, i. e., in alkaline or acidic media, to the extent ofat lea t 0.5%. Furthermore, they must be substantially inert chemicallytoward'and unaffected by the components of the viscose and of thecoagulating bath. Suitable agents which may be mentioned in addition tothose used in the examples are tetraethylammonium bromide,tetramethylammonium iodide, tetrapropylammonium hydroxide,tetrabutylammonium chloride, tributylpropylammonium hydroxide.tri(beta-hydroxyethyl) methylammo- 14 nium hydroxide.tributyl(beta-hydroxyethyl-am. monium iodide. etc.

As has been shown, the non-surface-active quaternary ammoniumcompoundsmay be used either in the viscose or in thecoagulating-regenerating bath. The agents may also be added to both theviscose and the bath in equal or different amounts, the totalconcentration being generally not more than about 10.0 millimoles pergrams of total solvent. In the latter event. the agent added to the bathmay be the same as or different than the agent added to the viscose. Foreffective results, there should be used at least 0.5 miliimole of agentper 100 grams of viscose or bath (the desirable concentration is aboutthe same in either case). 1 In general, it is unnecessary to use morethan 10 millimoles of the agent per 100 grams of solvent (viscose orbath), a. generally useful range being between about 0.9 and about 3.0millimoles per 100 grams. In terms of weightpercent basis, there shouldbe used between about 0.04% and about 0.3% of modifying agent, based oneither the viscose or bath. The optimum concentration for any givenagent depends on its effectiveness and on its molecular weight. It alsodepends to some extent on process variables such as the spinning speed,since at the high spinning speeds used in industrial practice, lessagent is desirable than at lower spinning speeds, for the reason thatthe rateof neutralization of the filament should be retarded only to theextent compatible with complete coagulation during the short time thefilament is in contact with the coagulating bath. Determination of theoptimum concentration of the quaternary ammonium compound is a matter ofsimple experimentation for those skilled in the art. In this connectionit should be pointed out that with ripened viscose there need be usedsomewhat less modifying agent than with unripened viscose, probablybecause the increase in alkali trithiocarbonate concentration whichaccompanies the ripening step tends to reinforce the effect of themodifying agent.

The viscose used in the process of the invention may be of a variety oftypes; for example, it may be from wood pulp, cotton linters, mixturesof the two, or even other types of cellulose. The composition of theviscose may also be varied widely. For example, it may have a cellulosecontent of from 4 to 10% or even more and an alkali content of from 4 to8% or more. The standard viscoses of the industry, i. e., those havingbetween 5 and 7% cellulose and between 4-6% alkali, are preferably used.The amount of carbon disulfide used in xanthation can be from 25-50%(based on the recoverable bone-dry cellulose). It has been found thathigher than normal xanthate sulfur contents (higher salt indices) can beused in the viscose when the short-chain quaternary am-. moniumcompounds described herein are added and there appears to be anadvantage in stretchability and level of yarn properties if salt indiceshigher than 5 are used. It is necessary to use 30% or greater amounts ofcarbon disulfide to obtain salt indices of 5 or over in unripznedviscoses. Thus, one of the chief advantages of the invention is thatunripened orpartiallv ripened viscoses may be used, with the result thatthe ripening time and space now required in viscose plants may beeliminated or substantially reducld. A very useful embodiment of theinvention is that illustrated in Example XII, wherein unripened viscoseis modified with a combination of a non-surface-active quaternaryammonium compound and added alkali trithiocarbonate. In such a case, anunexpected synergistic effect is observed as regards the neutralizationrate and the yarns are of remarkably high quality. As

specified in copending application Serial Number 656,478, alreadyreferred to, the quantity of alkali trithiocarbonate (e. g., sodium orpotassium trithiocarbonate) to be added to the green viscose need onlybe sufiicient to bring the total trithiocarbonate content to betweenabout 1% and about 3%, based on the viscose, which means in general thatthe amount added is between 0.2% and 2.25% of the weight of the viscose.

While the use of unripen d viscose is of'special interest in the processof this invention, it has been shown (Examples VIII and IX) that notableimprovements in yarn quality. are also obtained with normally ripenedviscose, thus making the process directly applicable to existing plantpractice.

The spinning baths suitable for use in the invention contain sulfuricacid, sodium sulfate, and zinc sulfate. Zinc sulfate is an essentialcom-' ponent of the spinning bath since, in its absence,

the quaternary ammonium compounds have no effect on spinning and yarnproperties. If desired, additional salts of divalent metals known toreinforce or supplement the action of zinc sulfate may be used, such asferrous sulfate, manganese sulfate, nickel sulfate, or chromic sulfate.Ferrous sulfate is particularly useful. Preferably, the spinning bathcontains from 4 to 12% of sulfuric acid, from 13 to 25% of sodiumsulfate, and from 1 to 15% of zinc sulfate, optionally including between0.8 and 6%, and preferably between 1% and 5%, of ferrous sulfate. Theoptimum quantity of zinc sulfate from the standpoint of practicalspinning speed appears to be 3 to 5%. With the addition of quaternaryammonium salts to viscose or spinning baths, it is 0 the basis ofavailable data, it is desirable to have the bath acidity andtemperatures as low as is practical for a given spinning speed in orderto get optimum filament structure and yarn properties. Each of the aboveconcentrations should be adjusted to each other and to the compositionof the viscose. It is desirable to use as high a total solids content aspossible in the coagulating bath to give the highest degree of gelshrinkage and improved stretchability.

The filaments may be" given a long travel of 50 130-250 inches in theprimary bath by means of a multiple roller setup which gradually appliestension to the traveling filaments and thereby orients them while theyare still plastic. The

preferred method, however, is to apply a part or 05 all of the stretchbeyond the primary bath in a secondary bath or to use a combination ofair and hot bath stretch. The secondary bath may consist simply of wateror of dilute (Ii-3%) sulfuric acid, or it may have the same compositionas the coagulating bath but at a greater dilution, e. g., one-fourth ofthe concentration of the coagulating bath. The temperature of thesecondary bath is preferably between 50 and 100 C. Stretches of til-100%are'preferred for producing high tenacity yarn and 20-30% for tax,-

tile type yarns. The bobbin process has been used in the examples, butit is immaterial whether spinning is by bobbin, bucket, or continuousprocesses. The yarn cake is washed free of acid and salt and then driedunder tension. If preferred, it may be twister or slasher-dried toenable the dry elongation of the finished product to be controlled. When.using the two-bath spinning system, the preferred procedure is to drawoff the freshly coagulated gel yarn with a feed wheel speed equal to orless than the jet velocity and to apply all of the stretch betweenpositively driven rollers traveling at different speeds. The thread canbe given a travel of 10-50 inches in the secondary bath of hot water ordilute bath. As mentioned above, the amount of stretch applied dependson the properties desired for the yarn.

0n the basis of available data, it is thought probable that themechanism by which quaternary ammonium compounds influence the spinningprocess is through interaction with zinc sulfate on the one hand andwith the sodium trithiocarhonate of the viscose on the other hand. Ithas-not yet been possible to determine whether this effect on filamentformation is accomplished through (1 buffer action, (2) transientformation of insoluble complexes, which might exercise some control onthe porosity of the initial skin which is set up, (3) ionbridgeformation, or (4) other colloidal effects.

The novel and improved yarns obtainable through the process of thisinvention can, in general be used instead of regular regeneratedcellulose fibers for anypurposes where the latter are findingapplications, more particularly in the textile and tire cord industries.

Any departure from the above description which conforms to the presentinvention is intended to be included within the scope of the claims.

I claim:

1. A method of producing regenerated cellulosic 4.) structures whichcomprises the step of spinning a viscose solution in a spinning bathcomprising an aqueous solution of sulfuric acid containing from 1% to15% zinc sulfate, the said spinning being conducted in the presence ofabout 0.5 to about 10.0 millimoles per grams of one of said solutions ofa water-soluble quaternary ammonium compound of the formula wherein R1,R2, R3, and R4 are organic groups which contain no more than fouraliphatic carbon atoms, at least three of the said groups contain onlyaliphatic carbon atoms and the fourth of the said groups contains nomore than one phenyl radical and where X- is an anion havingsubstantially no surface activity.

2. A method of producing regenerated cellulosic structures whichcomprisesthe step of spinning viscose in an aqueous sulfuric acidspinning bath containing from 1% to 15% zinc sulfate together with, per100 grams of bath, about 0.5 to about 10.0 millimoles of a water-solublequaternary ammonium compound of the formula 17 wherein R1, Re, R: and R4are aliphatic radicals. each of the said radicals containing no more"than 4 carbon atoms and xis an anion having substantially no surfaceactivity.

3. A process as defined in claim 2 in which the said structures arepassed into a second bath and subjected to a stretching treatment insaid second bath.

4. A method of producing regenerated cellulosic structures whichcomprises the step of spinning viscose in an aqueous sulfuric acidspinning bath containing from 1% to zinc sulfate, the said viscosecontaining, Der 100 grams of viscose, about 0.5 to about 10.0 millimolesof a water-soluble monium compound of the formula quaternary ammoniumcompound of the formula [Rails] wherein R1, Ra, Re and R4 are aliphaticradicals ach of the said radicals containing nomore than 4 carbon atomsand X in an anion having substantially no surface activity.

wherein R1, R2, and R3 are aliphatic radicals, each of the said radicalscontaining no more than 4 carbon atoms, the radical R4 containing nomore than 4 aliphatic carbon atoms and no more than 1 phenyl radical,and X- is an anion having substantially no surface activity.

7. A process as defined in claim 6 in which the said structures arepassed into a second bath and subjected to a stretching treatment insaid second bath.

8. A method of producing regenerated cellulosic structures whichcomprises the step of spinning viscose in an aqueous sulfuric acidspinning bath containing from 1% to 15% zinc sulfate, the said viscosecontaining, per 100 grams of viscose, about 0.9 to about 3.0 millimolesof a water-soluble quaternary ammonium compound of the formula whereinR1, R2 and R3 are aliphatic radicals, each of the said radicalscontaining no more than 4 carbon atoms, the radical R4 contains no morethan 4 aliphatic carbon atoms and no more than 1 phenyl radical, and Xis an anion having substantially no surface activity.

9. A process as defined in claim 8 in which the said structures arepassed into a second bath and subjected to a stretching treatment insaid second bath.

10-. A method of producing regenerated cellulosic structures whichcomprises the step of spinning viscose containing a water-solubletrithiocarbonate in addition to that formed during xanthation in anaqueous sulfuric acid bath con-- taining 1% to 15% zinc sulfate togetherwith grams of bath, the said quaternary ammonium compound correspondingto the formula [RP-E m];- it

wherein R1, Ra, Re and R4 are organic groups which contain no more thanfour aliphatic carbon atoms, at least three of the said groupscontaining only aliphatic carbon atoms, and the fourth of the saidgroups containing no more than one phenyl radical and whereas X- is ananion having substantially no surface-activity;

11. A process which comprises incorporating in viscose which contains awater-soluble trithiocarbonate in addition to that formed duringxanthation about 0.9 to about 3.0 millimoles of a water-soluble,quaternary ammonium compound per 100 grams of viscose and extruding theresultant viscose into a coagulating bath comprising an aqueous solutionof sulfuric acid and 1% to 15% zinc sulfate, the said quaternaryammoniumcompound corresponding to the formula [his]; l.

wherein R1, R2, R3 and R4 are organic groups which contain no more thanfour aliphatic carbon atoms, at least three of the said groups containing only aliphatic carbon atoms, and the fourth of the said groupscontaining no more than one phenyl radical and where X"- is an anionhaving substantially no surface-activity.

13. A process which comprises. incorporating in viscose containing analkali. metal trithiocarbonate in addition to that formed duringxanthation about 0.9 toabout 3.0 millimoles of a water-soluble,quaternary ammonium compound per 100 grams of viscose, extruding theresultant viscose into a coagulating bath comprising an aqueous solutionof 4% to 12% sulfuric acid, 13% to 25% sodium sulfate and 1% to 15% zincsulfate, the said quaternary ammonium compound corresponding to theformula [ails];- i.

wherein R1, R2, R3 and R4 are organic groups which contain no more thanfour aliphatic carbon phenyl radical and wherein X is an anion havingsubstantially no surface-activity.

14. A process according to claim 13 in which the coagulating bathcontains about 0.9 to about 3.0 millimoles of a water-soluble,quaternary ammonium compound per 100 grams of bath, the said quaternaryammonium compound corresponding to the formula wherein R1, R2, R3 and R4are organic groups which contain no more than four aliphatic carbonatoms, at least three of th said groups containing only aliphatic carbonatoms, and the fourth of the said groups containing no more than onephenyl radical and wherein X is an anion having substantially nosurface-activity.

15. An aqueoussulfuric acid spinning bath for the spinning ofregenerated cellulosic structures from viscose, said bath containingfrom 1% to 15% zinc sulfate together with about 0.5 to about 10.0millimoles of a water-soluble, quaternary ammonium compound per 100grams of bath, the said quaternary ammonium compound corresponding tothe formula wherein R1, R2, R3 and R4 are organic groups which containno more than four aliphatic carbon atoms, at least three of the saidgroups containing only aliphatic carbon atoms, and the fourth of thesaidgroups containing no more than one phenyl radical and wherein X" is ananion having substantially no surface-activity.

16. An aqueous sulfuric acid bath for the spinning of regeneratedcellulosic structures from viscose, said bath containing from 4% to 12%sulfuric acid, 13% to 25% sodium sulfate, 1% to 15% zinc sulfate andabout 0.9 to about 3.0 millimoles of a water-soluble, quaternaryammonium compound per 100 grams of bath, the said quaternary ammoniumcompound corresponding to the formula R: P [m-liLRJx- 4 wherein R1, R2,R3 and R4 are organic groups which contain no more than four aliphaticcarbon" atoms, at least three of the said groups containing onlyaliphatic carbon atoms, and the fourth of the said groups containing nomore than one phenyl radical and wherein X- is an anion havingsubstantially no surface-activity.

17. An aqueous sulfuric bath for the spinning of regenerated cellulosicstructures from viscose, said bath containing from 4% to 12% sulfuricacid, 13% to 25% sodium sulfate, 1% to 15% zinc sulfate, 1% to ferroussulfate and about 0.9 to about 3.0 millimoles of a water-soluble,quaternary ammonidm compound per 100 grams of bath, the said quaternaryammonium compound corresponding to the formula wherein R1, R2, R3 and R4are organic groups which contain no more than four aliphatic carbonatoms, at least three of the said groups containing only aliphaticcarbon atoms, and the fourth of the said groups containing no more thanone phenyl radical and wherein X- is an anion having substantially nosurface-activity.

18. A filament of regenerated cellulose having a smooth surface, showingno appreciable crenulation and having a core surrounded by a skin, theratio of th cross-sectional area of the skin to the core eing greaterthan one and the boundary therebetween being diffuse.

19. A filament of regenerated cellulose having a smooth surface, andshowing no appreciable crenulation, being composed of about 40% coresurrounded by about skin, the boundary therebetween being diffuse.

20. A filament in accordance with claim 18 characterized by a lateralorder of about 18.

21. A process in accordance with claim 1 in which the said quatenaryammonium compound is benzyltrimethylammonium hydroxide.

22. A \process in accordance with claim 1 in which the said quaternaryammonium compound is tetraethylammonium hydroxide.

23. A proczss is accordance with claim 1 in which the said quaternaryammonium compound is tetramethylammonium hydroxide.

NORMAN LOUIS COX.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,683,199 Lilienfeld Sept. 4,1928 2,125,031 Polak July 26, 1938 2,174,991 Masland Oct. 3, 19392,310,207 Bley Feb. 9, 1943 2,340,377 Graumann et al Feb. 1, 19442,345,570 Bley Apr. 4, 1944 2,373,712 Schlosser Apr. 17, 1945 2,412,969Cramer Dec. 24, 1946 2,517,694 Merion et a1 Aug. 8, 1950 FOREIGN PATENTSNumber Country Date 51,307 Netherlands Sept. 16, 1941 778,947 France 1Mar. 26, 1935 OTHER REFERENCES Berl et al.: "Cellulose Chemie, vol. VII,#10, pages 137 and 138, Oct. 3, 1926.

Rcinthaler: Artificial Silk, D. Van Nostrand Company, Incorporated, NewYork, 1928, page 138-147.

Certificate of Correction Patent No. 2,536,014 December 26, 1950 NORMANLOUIS 00X It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows:

Column 1, line 8, for the word or read of; column 4, lines 18 and 21,for the D value read the D calue; line 23, same column, for the D valueread the D value; line 26, for increased D value read increased D value;line 49, for viscos read 'v'iscose; column 6, line 13, for diffused readdi use; columns 5 and 6, Table IA, ,in the'heading to the last portionthereo for Na SO read Nw S0 columns 7 and 8, Table IB, first line underthe heading Density for 1.92 read 1.2.9; same line, under theheading,Orientation for 7.4 read 7.0; column 7,. line 45,'for 101 read101; line 7 4, for Warn read ya/m; column 8, Table III, column 9, TablesIV, V, and VI, under the heading Yarn Properties, seventh line,respectively, for Gel Swelling read Gel Swelling g.; column 10, TableVII, third column thereof, for Ripened read Um'ipe'lwd; Table VIII,second column, for Unripened read Ripened; column'12, line 7, for(8-15-15) read (8-14-15); column 14, line 1, forbeta-hydroxyethyl-amread betakydrowyethyl)-am- A and that the saidLetters Patent should be read as corrected above, so that the same mayconform to the record of the case in the Patent Olfice.

Signed and sealed this 29th day of May, A. "D. 1951.

THOMAS F. MURPHY,

Assistant of Patmta.

1. A METHOD OF PRODUCING REGENERATED CELLULOSIC STRUCTURES WHICHCOMPRISES THE STEP OF SPINNING A VISCOSE SOLUTION IN A SPINNING BATHCOMPRISING AN AQUEOUS SOLUTION OF SULFURIC ACID CONTAINING FROM 1% TO15% ZINC SULFATE, THE SAID SPINNING BEING CONDUCTED IN THE PRESENCE OFABOUT 0.5 TO ABOUT 10.0 MILLIMOLES PER 100 GRAMS OF ONE OF SAIDSOLUTIONS OF A WATER-SOLUBLE QUATERNARY AMMONIUM COMPOUND OF THE FORMULA